Hand-held power tools for tree care or hedge trimming have a pole, a power source such as an engine or an electric motor mounted at one end of the pole, and a tool such as a chain saw or a hedge trimmer driven by the power source and mounted at the other end of the pole. Examples of a pole saws are models 326P4 and 326P5x that are available from Husqvarna AB, and examples of pole hedge trimmers are models 326HE3x and 326HE4x, likewise available from Husqvarna AB (http://international.husqvarna.com). To relieve the arms of a user from the weight of the hand-held power tool, it is suspended in a harness worn by the user. However, when the power tool has a lifting eye located substantially at the center of gravity of the power tool in order to balance the weight of the power source against the weight of the tool, there usually will be too long a distance to a rear grip on the power source end of the pole to give a comfortable working position for the operator. Working with such hand-held power tools for tree care or hedge trimming at angles of 10 to 105 degrees from a vertical plane, will result in a very large load primarily on the other arm holding the tool in a second grip closer to the tool end of the pole, and long working periods will be impossible.
Harnesses, in which a hand-held power tool is intended to be suspended, are known in a variety of models. A harness developed for use with a clearing saw or the like is disclosed in U.S. Pat. No. 6,247,624 B1 (Rundberg) and includes a supporting rope having one end connected to a back plate of the harness and the other end connected to a breast plate of the harness. The rope passes slidingly through a tubular passage provided in a hip pad having a hook, from which the power tool is suspended.
U.S. Pat. No. 2,208,962 (de Finetti) discloses a load bearing apparatus for transport on shoulders, and U.S. Pat. No. 3,327,788 (Kolpe) discloses a harness for an earth boring machine, where the load bearing apparatus of the '962 patent appears to be included in the harness.
DE 667 986 (Bräuer) discloses another load bearing apparatus for mechanically powered tools, where the tool is suspended in a rubber rope extending through a steel tube, which is fixed to a rear portion of a waist strap of a harness and curves over a shoulder of the tool operator.
SE 54 783 (Goldschmidt) discloses another apparatus for facilitating the use of comparatively heavy hand-held tools, particularly mechanically powered hand-held hammers. This apparatus is connected to the tool as well as to a part of the operator's body, in a way that when the operator presses the tool against a workpiece by means of the apparatus, the apparatus will also exert a lifting force on the tool.
UK patent application GB 2 399 564 A (Prosser) relates to a safety system, particularly suitable for workers in the building trade and comprises a housing, which is secured to a belt or harness worn by the worker. Each housing comprises a reel, on which a flexible cord is wound. Means are provided for releasably securing the flexible cords to the tools.
The cord may be unwound from the reel, so that the tool can be used, and then the cord is automatically rewound onto the reel, when the external force on the cord is released. The reel may be controlled by a spring secured to the housing. Means are preferably provided for locking the reel mechanism after the cord has been extended. This safety system reduces the risk of persons being injured by tools dropped from a substantial height.
U.S. Pat. No. 2,282,653 (Herzmark) discloses a surgical traction tool of a design that makes it useful as an aid in maintaining a tool oriented in a desired position. The apparatus has a strap reeled on a drum, inside which a flat coiled spring is located. Further, the apparatus has a rotatable lever, by means of which by means of which the amount of tension applied to the coiled spring may be adjusted, independent of the unwound length of the strap.
An other type of mechanism for paying out a desired length of a strap or the like and then rewinding it by means of a tensioned spring is used in safety belts for vehicles, particularly motor cars, see U.S. Pat. No. 4,290,564 (Karlsson), for example.